The so-called fountain-type soldering method is one in which a stream of molten solder is caused to gush upwards from a nozzle in the form of a fountain, and portions of a printed circuit board which require soldering are immersed in the stream which rises above the nozzle. By forming a large number of choppy waves in the stream of molten solder, the solder can be made to penetrate to all portions of the semiconductor chip and poorly soldered connections can be prevented.
As it is important to form choppy waves in the stream of molten solder, a soldering bath for use in this method is equipped with a suitable wave-making device.
There have been many different proposals concerning the structure of a soldering bath for the fountain-type soldering method and of a wave-making device for use in such a soldering bath. However, in all of these proposals, the wave-making device has a sliding or rotating member which is immersed in molten solder, and as a result the wave-making device is subject to frequent breakdowns. Furthermore, as it is necessary to provide drive mechanism for the wave-making device on the outside of the solder bath, the costs of the bath and the wave-making device are extremely high. Moreover, conventional wave-making devices are unable to produce a uniform stream of molten solder having sufficiently choppy waves in the surface thereof, and therefore high-quality soldering can not be performed.